非负的高精度整数类实现

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在一些竞赛中，经常会使用到一些高精度的大数据类，在这里我送给大家一个高精度的整数类

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <cstdlib>

using namespace std;

#define MAX 2000
//非负的大整数类
class Bigint
{
public:
int len;//长度
int data[MAX];//存储大整数
Bigint();
Bigint(const char *S);
Bigint(int num);
//operator
Bigint &operator =(const char *S);
Bigint &operator =(int num);
friend istream &operator >>(istream &in,Bigint &B);
friend ostream &operator <<(ostream &out,Bigint &B);
Bigint operator +(Bigint &B);
Bigint operator +=(Bigint &B);
Bigint operator -(Bigint &B);
Bigint operator -=(Bigint &B);
bool operator > (Bigint &B);
Bigint operator *(int n);
Bigint operator *(Bigint &B);
//str
string str();
//赋值为n的阶乘
void assignf(int n);
};
Bigint::Bigint()
{
this->len = 0;
memset(this->data,0,sizeof(this->data));
}
Bigint::Bigint(const char *S)
{
this->len = strlen(S);//先给字符串长度赋值
int i;
for(i=0;i<len;i++)
{
this->data[i] = S[len-1-i]-'0';//从低位到高位赋值
}
}
Bigint::Bigint(int num)
{
char S[14];
sprintf(S,"%d",num);//将整数变成字符串打印到内存中
this->len = strlen(S);//同上
int i;
for(i=0;i<len;i++)
{
this->data[i] = S[len-1-i]-'0';
}
}
Bigint& Bigint::operator =(const char *S)
{
this->len = strlen(S);
int i;
for(i=0;i<len;i++)
{
this->data[i] = S[len-1-i]-'0';
}
return *this;
}
Bigint& Bigint::operator =(int num)
{
char t[14];
sprintf(t,"%d",num);
*this = t;
return *this;
}
//返回字符串形式的整形
string Bigint::str()
{
string S;
int i;
for(i=0;i<this->len;i++)
{
S = (char)(this->data[i]+'0')+ S;
}
return S;
}
istream &operator >>(istream &in,Bigint &B)
{
string S;
in>>S;
B = S.c_str();
return in;
}
ostream &operator <<(ostream &out,Bigint &B)
{
out<<B.str();
return out;
}
//整数的加操作
//首先从低位开始加，如果有进位就加到上一位，直到超出证书长度并且进位==0
Bigint Bigint::operator +(Bigint &B)
{
int maxlen = this->len>B.len?this->len:B.len;
Bigint T;//返回的大整数类型
T.len = 0;
int i,j;
int t=0;
for(i=0,j=0;j||i<maxlen;i++)
{
//j是进位
t = j;//本位
if(i<B.len)
t+=B.data[i];
if(i<this->len)
t+=this->data[i];
T.data[T.len++] = t%10;//本位的值
j = t / 10;//进位
}
return T;
}
Bigint Bigint::operator +=(Bigint &B)
{
*this = *this+B;
return *this;
}
//a>b的情况,这里是一个计算非负数计算的类
//就像减法运算法则一样
//低位开始相减去，如果不够的话就向高位去借
Bigint Bigint::operator -(Bigint &B)
{
//返回的Bigint类
Bigint T;
T.len = 0;
int maxlen = this->len>B.len?this->len:B.len;
int i,j;
for(j=0,i=0;i<maxlen||j;i++)
{
//j是借位
//temp是本位
int temp = this->data[i] - B.data[i] - j;
if(temp>=0)
{
T.data[T.len++] = temp;
j=0;
}
else
{
T.data[T.len++] = temp+10;
j = 1;
}
}
return T;
}
Bigint Bigint::operator -=(Bigint &B)
{
Bigint T;
T.len = 0;
int i,j;
int maxlen = this->len>B.len?this->len:B.len;
for(i=0,j=0;j||i<maxlen;i++)
{
int temp = this->data[i]-B.data[i]-j;
if(temp>=0)
{
this->data[i] = temp;
j=0;
}
else
{
this->data[i] = temp + 10;
j=1;
}
}
return *this;
}
//判断大小
//如果长度不一样的话，直接判断
//否则从高位开始比较
bool Bigint::operator > (Bigint &B)
{
int i;
if(this->len>B.len)
return true;
else if(this->len<B.len)
return false;
else
{
for(i=this->len-1;i>=0;i--)
{
if(this->data[i] != B.data[i])
return this->data[i] > B.data[i];
}
}
return false;
}
void Bigint::assignf(int n)
{
int temp;
int c;
int i,j;
memset(this->data,0,sizeof(this->data));
this->len = 0;
this->data[0] = 1;//0或者1的阶乘是1
for(i=2;i<=n;i++)
{
//将这个整数乘以i
c = 0;//进位
for(j=0;j<MAX;j++)
{
temp = this->data[j]*i+c;
this->data[j] =temp%10;
c = temp/10;
}
}
for(i=MAX-1;;i--)
{
if(this->data[i])
{
this->len = i+1;
break;
}
}
}
Bigint Bigint::operator *(int n)
{
int temp;
int c;//进位
Bigint T = *this;
int i;
for(i=0,c=0;i<this->len||c;i++)
{
temp = T.data[i]*n+c;
T.data[i] = temp%10;
c = temp/10;
}
for(i=MAX-1;;i--)
{
if(T.data[i])
{
T.len = i+1;
break;
}
}
return T;
}
Bigint Bigint::operator *(Bigint &B)
{
int i,j;
Bigint T;
Bigint R;
for(i=0;i<B.len;i++)
{
T = ((*this) * (B.data[i]));
R+=T;
}
return T;
}
int main()
{
Bigint B2 = "2";
Bigint B3;
B3.assignf(4);
B3 = B3*B2;
cout<<B3.str();
return 0;
}

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